Lens holder driving device and camera-equipped portable terminal

ABSTRACT

A lens holder driving device is provided with a lens holder, a securing part including a base member, a drive mechanism, and a position detection unit. The drive mechanism includes a yoke that is provided to stand on the base member. The position detection unit includes a sensor magnet mounted to the outer peripheral surface of the lens holder, and a magnetic detection element provided in the securing part. The yoke is provided with a tube-shaped external cylinder part, and the external cylinder part includes a plurality of plate sections each having a cutout section. The lens holder driving device includes a foreign matter entry prevention member that prevents foreign matter from getting inside from the cutout sections of the plate sections.

TECHNICAL FIELD

The present invention relates to a lens holder driving device, andparticularly relates to a lens holder driving device and acamera-equipped mobile terminal in which a lens holder (movable part) towhich a lens barrel can be attached can move in a light axis directionof a lens.

BACKGROUND ART

A small-sized mobile camera is installed in a camera-equipped mobileterminal. In this small-sized mobile camera, an auto focus (AF) lensholder driving device is used. VCM systems using a voice coil motor(VCM) are known as a driving mechanism (actuator) used for theabove-mentioned AF lens holder driving device. An AF lens holder drivingdevice of the VCM type includes a magnetic circuit composed of a drivingcoil, a yoke and a permanent magnet as a driving mechanism (actuator).The driving mechanism of the VCM type is roughly categorized into thedriving mechanism of “moving coil type” and the driving mechanism of“moving magnet type.”

An AF lens holder driving device of the VCM type employs a spring member(elastic member) that supports a columnar movable part including a lens(a lens and a lens holder) such that the movable part is displaceable inthe light axis direction (center axis direction) in a state where theposition of the movable part in the radial direction with respect to thefixing part is set. It is to be noted that the movable part is alsoreferred to as moving body, movable body, or lens fixing body, and thefixing part is also referred to as fixing member, supporting body,housing, or fixing body. The above-mentioned driving mechanism isprovided in the movable part (moving body) and the fixing part (fixingmember; supporting body).

As the above-mentioned spring member (elastic member), in general, apair of leaf springs which are provided on the both sides in the lightaxis direction of a lens holder (columnar movable part; moving body)that holds a lens assembly (lens barrel) are used. The pair of leafsprings supports the lens holder (columnar movable part; moving body)such that the lens holder (columnar movable part; moving body) isdisplaceable in the light axis direction in a state where the positionin the radial direction of the lens holder is set with respect to thehousing (cylindrical fixing part; fixing member; supporting body)disposed at the periphery thereof. One of the pair of leaf springs isreferred to as upper leaf spring, and the other is referred to as lowerleaf spring.

It is to be noted that the upper leaf spring is also referred to asfront spring or front spring member, and the lower leaf spring is alsoreferred to as rear spring or rear spring member.

With the above-mentioned configuration, in an AF lens holder drivingdevice of the VCM type, the restoration force (biasing force) of theleaf spring (spring member) and the thrust (driving force) of thedriving mechanism are balanced, and the movable part (moving body) ismoved to a predetermined position (target position) in the light axisdirection. In the AF lens holder driving device of the VCM type havingsuch a configuration, the movable part (moving body) is supported withthe leaf spring (spring member) with respect to the fixing part (fixingmember; housing; supporting body), and therefore the movable part(moving body) is vibrated more than necessary by driving of the movablepart (moving body), or by vibration, impact and the like from theoutside.

In view of this, a position detection part (position detectionmechanism; position detection means) is provided to the lens holderdriving device to control (adjust) the position of the movable part byfeedback control. Conventionally, various position detection parts havebeen proposed.

For example, PTL 1 discloses a lens driving device that performs handshake correction by utilizing a position detection mechanism using aHall device sensor magnet and a Hall device sensor. The lens drivingdevice disclosed in PTL 1 includes a cylindrical lens supporting body,an annular yoke, and a plurality of driving magnets. The cylindricallens supporting body extends in the longitudinal direction and the coilis placed on the outer periphery side. The yoke is placed on the outsideof the lens supporting body in the radial direction. The driving magnetsare respectively placed at positions on the inside of the externalperipheral wall of the annular peripheral wall of the yoke and theoutside of the coil in the radial direction with a predetermineddistance from the coil. In addition, the driving magnets are placed witha predetermined distance from the adjacent driving coil in thecircumferential direction of the yoke.

In PTL 1, the Hall device sensor magnet is placed at the lens supportingbody at a position between adjacent two driving magnets in thecircumferential direction of the yoke in the driving magnets. The Halldevice sensor is placed to a base to which the yoke and the lenssupporting body are installed. A cutout part is formed in the drivingmagnet at the side surface opposite to the adjacent driving magnet.

PTL 2 discloses an image pickup device including an actuator and aposition detection part. The actuator is composed of a coil attached ona driven surface of a movement cylindrical body that holds a pluralityof lenses, a magnet opposite to the coil, and a yoke disposed at theperiphery of the magnet. The position detection part is composed of oneHall device magnet attached on the movement cylindrical body, and a Halldevice provided on an assembly housing side opposite to the movementcylindrical body and configured to detect the magnetic force of the Halldevice magnet to perform position detection.

PTL 3 discloses a lens driving device including an actuator and aposition detection means. The actuator includes a coil body fixed at theouter periphery of a lens supporting body that supports a lens at theinner periphery, a yoke that movably supports the lens supporting body,and four driving magnets fixed at corner portions of the outer peripheryside wall of the yoke. The inner periphery side of each driving magnethas an arc-like shape extending along the outer peripheral surface ofthe coil.

In addition, in the third embodiment in PTL 3, the position detectionmeans that detects the position of the lens supporting body with respectto the fixing body in the X direction, the Y direction and the Zdirection is composed of a X-direction position detection magnet, aY-direction position detection magnet, and a Z-direction positiondetection magnet disposed on the side surface of the lens supportingbody, and, a X-direction position detection device, a Y-directionposition detection device, and a Z-direction position detection devicedisposed on the external surface of the lens driving device so as to berespectively opposite to the direction position detection magnets. Thecircuit board in which the position detection devices are installed areprovided on the outer periphery side of the lens driving device.

CITATION LIST Patent Literature PTL 1 Japanese Patent ApplicationLaid-Open No. 2013-33179 PTL 2 Japanese Patent Application Laid-Open No.2007-121850 (FIG. 3, [0023] and [0024]) PTL 3 Japanese PatentApplication Laid-Open No. 2012-177753 (FIG. 9 to FIG. 14, [0069])SUMMARY OF INVENTION Technical Problem

The position detection mechanism disclosed in PTL 1 detects the positionin the X axis direction and the Y-axis direction orthogonal to theoptical axis (Z axis) of the lens supporting body, not the position inthe light axis direction (the Z-axis direction) of the lens supportingbody. That is, with the configuration of the position detectionmechanism disclosed in PTL 1, the position in the light axis direction(the Z-axis direction) of the lens supporting body cannot be detected.

In the position detection part disclosed in PTL 2, only one Hall devicemagnet is attached to the movement cylindrical body, and consequentlythe gravity center of the moving body (the lenses, the movementcylindrical body, the coil, and the Hall device magnet) is shifted fromthe optical axis. As a result, with an image pickup device including theposition detection part disclosed in PTL 2, it is difficult to stablydrive the moving body with a good balance.

In the lens driving device disclosed in PTL 3, the circuit board inwhich the position detection device is installed is provided on theouter periphery side of the lens driving device, and consequentlyforeign matter such as dust may possibly intrude into the lens drivingdevice through the gap.

Accordingly, an object of the present invention is to provide a lensholder driving device having an enclosed structure which can preventintrusion of foreign matter such as dust.

Other objects of the present invention will be apparent from thefollowing descriptions.

Solution to Problem

In an exemplary mode of the present invention, a lens holder drivingdevice includes: a lens holder to which a lens barrel is attachable; afixing part disposed at an outer periphery of the lens holder; a drivingmechanism for driving the lens holder in a direction of an optical axisof a lens; and a position detection part configured to detect a positionof the lens holder in the direction of the optical axis. The fixing partincludes a base member disposed on a lower side of the lens holder. Thedriving mechanism includes a yoke uprightly provided on the base member.The position detection part includes a sensor magnet attached on acorresponding outer peripheral surface of the lens holder in a directionorthogonal to the optical axis, and a magnetic detection device providedto the fixing part such that the magnetic detection device is oppositeto the sensor magnet. The yoke includes an outer cylinder part having acylindrical shape, and the outer cylinder part includes a plurality ofplate parts which are opposite to each other in the direction orthogonalto the optical axis, the plate parts having cutout parts at positionsopposite to the sensor magnet. The lens holder driving device includes aforeign matter intrusion prevention member configured to preventintrusion of foreign matters from the cutout part of the plate part.

Advantageous Effects of Invention

According to the present invention, intrusion of foreign matter such asdust can be prevented.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an external appearance of a lens holderdriving device according to a first embodiment of the present invention;

FIG. 2 is an exploded perspective view of the lens holder driving deviceillustrated in FIG. 1;

FIG. 3 is a longitudinal sectional view taken along the line of FIG. 1;

FIG. 4 is a longitudinal sectional view taken along the line IV-IV ofFIG. 1;

FIG. 5 is a plan view illustrating a shape of an upper leaf spring usedfor the lens holder driving device illustrated in FIG. 1 as viewed froma base member;

FIG. 6 is a plan view illustrating a shape of a lower leaf spring usedfor the lens holder driving device illustrated in FIG. 1 as viewed frombase member;

FIG. 7 is a plan view illustrating a relationship between the upper leafspring illustrated in FIG. 5 and the lower leaf spring illustrated inFIG. 6;

FIGS. 8A and 8B are drawings for describing a conductor pattern formedin a flexible printed circuit (FPC) used for the lens holder drivingdevice illustrated in FIG. 1, FIG. 8A being a front view of the lensholder driving device; FIG. 8B showing a relationship between seventerminals of the conductor pattern of flexible printed circuit (FPC) andterminals connected to the seven terminals;

FIG. 9 is a plan view illustrating an assembly of the lens holderdriving device illustrated in FIG. 1 as viewed from the base member, andillustrates a state before an elastic adhesive agent is provided(applied) to the lower leaf spring;

FIG. 10 is a plan view illustrating the assembly of the lens holderdriving device illustrated in FIG. 1 as viewed from the base member, andillustrates a state after the elastic adhesive agent is provided(applied) to the lower leaf spring;

FIG. 11 is a partially enlarged view illustrating a part of FIG. 9 in anenlarged manner;

FIG. 12 is a partially enlarged view illustrating a part of FIG. 10 inan enlarged manner;

FIG. 13 is a front view of the lens holder driving device illustrated inFIG. 1;

FIG. 14 is a back view of the lens holder driving device illustrated inFIG. 1;

FIG. 15 is a perspective view of a yoke used for the lens holder drivingdevice illustrated in FIG. 1;

FIG. 16 is a front view of the yoke used for the lens holder drivingdevice illustrated in FIG. 1;

FIG. 17 is a perspective view illustrating an assembly in which a spacer(inner housing), a driving magnet and an upper leaf spring are installedto the yoke in the lens holder driving device illustrated in FIG. 1;

FIG. 18 is a perspective view illustrating an assembly in which theupper leaf spring is installed to the spacer (inner housing) in the lensholder driving device illustrated in FIG. 1;

FIG. 19 is a longitudinal sectional view taken along the line IV-IV ofFIG. 1;

FIG. 20 is a cross-sectional perspective view specifically illustratinga part of (front side) a cross-section of FIG. 19;

FIG. 21 is a cross-sectional perspective view specifically illustratinga part (rear side) of the cross-section of FIG. 19;

FIG. 22 is a perspective view of the lens holder driving deviceillustrated in FIG. 1 in which a flexible printed circuit (FPC) isomitted;

FIG. 23A is a front view illustrating the flexible printed circuit (FPC)used for the lens holder driving device illustrated in FIG. 1;

FIG. 23B is a back view illustrating the flexible printed circuit (FPC)used for the lens holder driving device illustrated in FIG. 1;

FIG. 23C is a plan view (top view) illustrating the flexible printedcircuit (FPC) used for the lens holder driving device illustrated inFIG. 1;

FIG. 24A is a front view illustrating a base material of flexibleprinted circuit (FPC) illustrated in FIG. 23A;

FIG. 24B is a back view illustrating the base material of the flexibleprinted circuit (FPC) illustrated in FIG. 23B;

FIG. 25A is a front view illustrating a state where a hole sensor isinstalled to the flexible printed circuit (FPC) in the lens holderdriving device illustrated in FIG. 1;

FIG. 25B is a back view illustrating a state where the hole sensor isinstalled to the flexible printed circuit (FPC) in the lens holderdriving device illustrated in FIG. 1;

FIG. 25C is a plan view illustrating (top view) a state where the holesensor is installed to the flexible printed circuit (FPC) in the lensholder driving device illustrated in FIG. 1;

FIG. 25D is a perspective view as viewed from the front surface sideillustrating a state where the hole sensor is installed to the flexibleprinted circuit (FPC);

FIG. 25E is a perspective view as viewed from the back side illustratinga state where the hole sensor is installed to the flexible printedcircuit (FPC) in the lens holder driving device illustrated in FIG. 1;

FIG. 26 is a plan view that illustrates the lens holder driving deviceillustrated in FIG. 1 and a connection state of the flexible printedcircuit (FPC);

FIG. 27 is a partially enlarged cross-sectional perspective viewillustrating a region around cone-shaped depressions of the flexibleprinted circuit (FPC) of FIG. 26 in an enlarged manner;

FIG. 28 is a partially enlarged perspective view illustrating a regionaround a protrusion part of the yoke of FIG. 26 in an enlarged manner;

FIG. 29 is a perspective view of the lens holder driving deviceillustrated in FIG. 1;

FIG. 30 is a partially enlarged view illustrating an abutting portion ofan upper leaf spring and a ring-shaped upper end part of the yoke ofFIG. 29 in an enlarged manner;

FIG. 31 is a perspective view of the spacer (inner housing) used for thelens holder driving device illustrated in FIG. 1;

FIG. 32 is a partially enlarged view illustrating a part of FIG. 31 inan enlarged manner;

FIG. 33 is a perspective view illustrating a camera-equipped mobileterminal in which the lens holder driving device illustrated in FIG. 1is installed;

FIG. 34 is a perspective view of a lens holder driving device accordingto a second embodiment of the present invention in which the yoke, theupper leaf spring, and the spacer (inner housing) are omitted;

FIG. 35 is a plan view of the lens holder driving device illustrated inFIG. 34;

FIG. 36 is a perspective view of a lens holder driving device accordingto a third embodiment of the present invention in which the yoke, theupper leaf spring, and the spacer (inner housing) are omitted; and

FIG. 37 is a plan view of the lens holder driving device illustrated inFIG. 36.

DESCRIPTION OF EMBODIMENTS

In the following, embodiments of the present invention are describedwith reference to the accompanying drawings.

First Embodiment

With reference to FIG. 1 to FIG. 4, lens holder driving device 10according to a first embodiment of the present invention is described.

FIG. 1 is a perspective view illustrating an external appearance of lensholder driving device 10. FIG. 2 is an exploded perspective view of lensholder driving device 10. FIG. 3 is a longitudinal sectional view takenalong the line of FIG. 1. FIG. 4 is a longitudinal sectional view takenalong the line IV-IV of FIG. 1.

Here, as illustrated in FIG. 1 to FIG. 4, an orthogonal coordinatesystem (X, Y, Z) is used. In the orthogonal coordinate system (X, Y, Z)of FIG. 1 to FIG. 4, the X-axis direction is the front-rear direction(depth direction), the Y-axis direction is the horizontal direction(width direction), and the Z-axis direction is the vertical direction(height direction). In addition, in the example illustrated in FIG. 1 toFIG. 4, vertical direction Z is the direction of optical axis O of thelens. It is to be noted that, in the present embodiment, the Y-axisdirection (horizontal direction) is also referred to as first direction,and the X-axis direction (front-rear direction) is also referred to assecond direction.

It should be noted that, when actually used, the direction of opticalaxis O, that is, the Z-axis direction is the front-rear direction. Inother words, the upward direction of the Z axis is the forwarddirection, and the downward direction of the Z axis is the rearwarddirection.

Lens holder driving device 10 illustrated in the drawing is a lensholder driving device that employs a voice coil motor (VCM) system usinga VCM as the driving mechanism (actuator). The lens holder drivingdevice of the VCM type includes a driving coil, and a magnetic circuitcomposed of a yoke and a permanent magnet as the driving mechanism(actuator) as described later. Lens holder driving device 10 illustratedin the drawing employs a driving mechanism of “moving coil type” as thedriving mechanism of the VCM type.

Lens holder driving device 10 illustrated in the drawing is used in amobile terminal capable of performing auto focus (AF) such as acamera-equipped mobile phone, a smartphone described later illustratedin FIG. 33, a note-type personal computer, a tablet-type personalcomputer, a mobile game machine, a Web camera, and an in-vehicle camera.

Lens holder driving device 10 illustrated in the drawing is intended formoving lens holder 14 (described later) that holds lens barrel 11 in thedirection of optical axis O. Accordingly, optical axis O is the drivingaxis (central axis). Lens holder driving device 10 includes base member(actuator base) 12 disposed on the lower side (rear side) in the Z-axisdirection (the direction of optical axis O).

At a lower portion (rear portion) of base member (actuator base) 12, asensor substrate (not illustrated) is disposed. On the sensor substrate,electronic components such as an imaging device and a clock generationsource are installed. Lens holder driving device 10 and the sensorsubstrate are covered with a shield case (not illustrated). The shieldcase blocks electromagnetic noise generated by the sensor substrate.

A camera module is composed of a combination of lens holder drivingdevice 10, the sensor substrate, the imaging device, and the shieldcase.

The imaging device captures a subject image imaged by lens barrel 11 andconverts the image into an electric signal. The imaging device iscomposed of, for example, a charge coupled device (CCD) image sensor, acomplementary metal oxide semiconductor (CMOS) image sensor or the like.

Lens holder driving device 10 includes: lens holder 14 includingcylindrical part 140 for holding lens barrel 11; ring-shaped drivingcoil 16 fixed to lens holder 14 such that it is located at the outerperiphery of cylindrical part 140; yoke 20 having a substantiallyquadrangular cylindrical shape including driving magnet 18 that isopposite to driving coil 16; and a pair of leaf springs 22 and 24provided on both sides of cylindrical part 140 of lens holder 14 in thedirection of optical axis O.

To attach lens barrel 11 to lens holder 14, lens barrel 11 is housed inlens holder 14, and lens barrel 11 and lens holder 14 are joined to eachother with adhesive agent or the like.

In addition, the magnetic circuit is composed of a combination ofdriving magnet 18 and yoke 2.

The pair of leaf springs 22 and 24 supports lens holder 14 such thatlens holder 14 is displaceable in the direction of optical axis O whilesetting the position of lens holder 14 in the radial direction.Regarding the pair of leaf springs 22 and 24, leaf spring 22 is referredto as upper leaf spring, and leaf spring 24 is referred to as lower leafspring.

In addition, as described above, when actually used, the upwarddirection of the Z-axis direction (the direction of optical axis O) isthe forward direction, and the downward direction of the Z-axisdirection (the direction of optical axis O) is the rearward direction.Accordingly, upper leaf spring 22 is also referred to as front spring,and lower leaf spring 24 is also referred to as rear spring.

Upper leaf spring (front spring) 22 and lower leaf spring (rear spring)24 are formed of a metal such as stainless steel, beryllium copper andnickel copper. In addition, upper leaf spring (front spring) 22 andlower leaf spring (rear spring) 24 is manufactured by working such asetching using photolithographic technique and pressing with apredetermined thin plate. Regarding the working, etching is preferablethan pressing.

The reason for this is that no residual stress is left in the leafspring which has been subjected to etching.

In addition, preferably, the material of the leaf spring is stainlesssteel, or in particular, high-hardness stainless steel than berylliumcopper. The reason for this is that a compound of beryllium is known tobe highly toxic, and it is desirable to use materials other thanberyllium copper as the material of the leaf spring (beryllium free)from the standpoint of environmental conservation. It is to be notedthat as the high-hardness stainless steel, NTK S-4 or NTK 301 (SUS301)available from Nippon Metal Industry Co., Ltd. may be used.

As illustrated in FIG. 1 and FIG. 2, yoke 20 has a substantiallyquadrangular cylindrical shape. That is, yoke 20 includes outer cylinderpart 202 having a substantially square cylindrical shape, and upper endportion 204 having a substantially quadrangular ring shape protruding tothe inner side of outer cylinder part 202 at the upper end (front end)of outer cylinder part 202. In addition, at the four corners of theinner side of ring-shaped upper end part 204, yoke 20 includes fourinner vertical extending parts 206 extending perpendicularly downward ina direction parallel to optical axis O.

Accordingly, driving coil 16 also has a substantially quadrangularcylindrical shape that matches the substantially quadrangularcylindrical shape of yoke 20. Specifically, driving coil 16 has anoctagonal cylindrical shape with four long side parts 162 disposed to beparallel to and opposite to the four sides of yoke 20, and four shortside parts 164 that are opposite to the four corners of yoke 20. Drivingcoil 16 is attached to the exterior wall of cylindrical part 140 of lensholder 14 in a region on a side closer to upper leaf spring 22 such thatdriving coil 16 is housed in a space between outer cylinder part 202 ofyoke 20 and four inner vertical extending parts 206.

As illustrated in FIG. 2 and FIG. 3, driving magnet 18 illustrated inthe drawing is composed of two plate-shaped driving magnet pieces 182that are disposed at two inner wall surfaces of outer cylinder part 202of yoke 20 which are opposite to each other in horizontal direction Ysuch that two plate-shaped driving magnet pieces 182 are opposite todriving coil 16 with a space therebetween. In other words, eachplate-shaped driving magnet piece 182 is extended such that the bothends thereof in the horizontal direction are located at a region closeto the two sides of yoke 20 opposite to each other in the front-reardirection X. In addition, driving coil 16 is disposed such that it isclose to a region around the both ends of each plate-shaped drivingmagnet piece 182 in the horizontal direction.

With this structure, reduction in the magnetic efficiency of themagnetic circuit can be suppressed.

Each plate-shaped driving magnet piece 182 is magnetized in the radialdirection, and the inner periphery side and the outer periphery sidethereof are magnetized in different polarities. In the exampleillustrated in the drawing, each plate-shaped driving magnet piece 182is magnetized such that the inner periphery side is magnetized to Npole, and the outer periphery side is magnetized to S pole asillustrated in FIG. 3.

The driving mechanism of “moving coil type” is composed of thecombination of driving coil 16, two plate-shaped driving magnet pieces182 and yoke 20.

Outer cylinder part 202 of yoke 20 is composed of front plate part 202Fand rear plate part 202B that are opposite to each other in front-reardirection X, and left plate part 202L and right plate part 202R that areopposite to each other in horizontal direction Y. Front plate part 202Fincludes front cutout part 202 a that opens downward, and rear platepart 202B includes rear cutout part 202 b that opens downward. Frontplate part 202F includes protrusion part 207 that protrudes downward atfront cutout part 202 a. Front plate part 202F is also referred to asfirst plate part, and rear plate part 202B is also referred to as secondplate part. In addition, front cutout part 202 a is also referred to asfirst cutout part, and rear cutout part 202 b is also referred to assecond cutout part.

On the other hand, base member (actuator base) 12 includes base part 120having a rectangular ring-shape, and a pair of protruding parts 122 and123 that are opposite to each other in front-rear direction X andprotrude upward in vertical direction Z from base part 120. Here,protruding part 122 provided on the front side is referred to as frontprotruding part, and protruding part 123 provided on the rear side isreferred to as rear protruding part. In addition, front protruding part122 is also referred to as first protruding part, and rear protrudingpart 123 is also referred to as second protruding part.

Lens holder driving device 10 illustrated in the drawing furtherincludes spacer 30 provided between base member (actuator base) 12 andyoke 20. Spacer 30 is also referred to as inner housing. Spacer (innerhousing) 30 has a shape which is substantially housed in the inner wallsurface of yoke 20. To be more specific, spacer (inner housing) 30includes: ring-shaped part 302 having a rectangular external shapeprovided at the upper portion of the inner wall surface of outercylinder part 202 of yoke 20; four vertical extending parts 304perpendicularly extending in a downward direction parallel to opticalaxis O from the four corners of ring-shaped part 302; and a pair ofU-shaped plate parts 305 and 306 extending in a downward directionparallel to optical axis O from a pair of the sides of ring-shaped part302 which are opposite to each other in front-rear direction X.

Here, U-shaped plate part 305 provided on the front side is referred toas front U-shaped plate part, and U-shaped plate part 306 provided onthe rear side is referred to as rear U-shaped plate part. In addition,front U-shaped plate part 305 is also referred to as first U-shapedplate part, and rear U-shaped plate part 306 is also referred to assecond U-shaped plate part.

The fixing part (12, 30) is composed of the combination of base member(actuator base) 12 and spacer (inner housing) 30.

As illustrated in FIG. 2 and FIG. 4, in a region around front cutoutpart (first cutout part) 202 a of yoke 20, front protruding part (firstprotruding part) 122 of base member 12 and front U-shaped plate part(first U-shaped plate part) 305 of spacer (inner housing) 30 are engagedwith each other (in engagement). In addition, in a region around rearcutout part (second cutout part) 202 b of yoke 20, rear protruding part(second protruding part) 123 of base member 12 and rear U-shaped platepart (second cutout part) 306 of spacer (inner housing) 30 are engagedwith each other (in engagement).

It is to be noted that front protruding part (first protruding part) 122of base member 12 has rectangular hole 122 a through which hole sensor344 that is the magnetic detection device described later is inserted.In addition, cylindrical part 140 of lens holder 14 includes a pair ofhousing parts 140 a for housing a pair of sensor magnets 342 a and 342 bdescribed later at lower portions of the exterior walls opposite to eachother in front-rear direction X with the Z axis (optical axis O) as thecenter.

Lens holder driving device 10 illustrated in the drawing furtherincludes position detection part 34 that detects the position of lensholder 14 in the direction of optical axis O.

As illustrated in FIG. 2 and FIG. 4, position detection part 34 isprovided in a region on a side closer to lower leaf spring 24. To bemore specific, position detection part 34 includes one of the pair ofsensor magnets 342 a and 342 b housed in the above-mentioned pair ofhousing parts 140 a of cylindrical part 140 of lens holder 14 (in theexample illustrated in the drawing, front side sensor magnet 342 a), andhole sensor 344 that is inserted in rectangular hole 122 a of basemember 12 in such a manner as to be opposite to sensor magnet 342 a.

Sensor magnets 342 a and 342 b are magnetized in the direction ofoptical axis O, and the top surface side and the bottom surface sidethereof are magnetized in different polarities. In the exampleillustrated in the drawing, each of sensor magnets 342 a and 342 b ismagnetized such that the top surface side is magnetized to S pole, andthe bottom surface side is magnetized to N pole as illustrated in FIG.4.

In the first embodiment, permanent magnets whose Curie point is 400° C.or above are used as sensor magnets 342 a and 342 b. Examples of such apermanent magnet include a samarium-cobalt magnet, a ferrite magnet, andan alnico magnet. With this configuration, thermal demagnetization ofsensor magnets 342 a and 342 b when in use can be suppressed.

As described, in the first embodiment, driving magnets 18 and the pairof sensor magnets 342 a and 342 b of position detection part 30 areseparated from each other. Accordingly, position detection part 34 canbe prevented from being negatively influenced by the magnetic fluxgenerated at driving magnet 18. As a result, position detection part 34can correctly detect the position of lens holder 14 in the direction ofoptical axis O.

In addition, in the first embodiment, as illustrated in FIG. 3 and FIG.4, by optimizing the polarity of two plate-shaped driving magnet pieces182 and the polarity of the pair of sensor magnets 342 a and 342 b, theinterference therebetween can be effectively used. To be more specific,yoke 20 itself is set to S pole when driving magnet 18 is disposed onthe inner wall surface of yoke 20. When the side (upper side) of sensormagnets 342 a and 342 b closer to yoke 20 is set to S pole, the initialposition is set by the balance with the spring force of leaf springs 22and 24 although slight magnetic interference (repulsion direction)exists. Assuming that the upper side of sensor magnets 342 a and 342 bis set to N pole, the attraction with yoke 20 is large, and the initialposition is unstable.

It is to be noted that the magnetic interference is small when themagnetic force of sensor magnets 342 a and 342 b is set to a smallvalue. With such a configuration, however, the output of hole sensor 344is also small, and the S/N ratio of the output of hole sensor 344 isdeteriorated. Accordingly, it is desirable to dispose sensor magnets 342a and 342 b at positions remote from yoke 20, and the position of holesensor 344 is optimally set with the influence of the magneticinterference included. That is, it is desirable to dispose sensormagnets 342 a and 342 b at positions which are remote from yoke 20 asmuch as possible, and are farthest from driving magnet 18.

Further, since the pair of sensor magnets 342 a and 342 b are disposedat positions which are point symmetrical about optical axis O, thedynamic balance with lens holder driving device 10 can be ensured. As aresult, the movable part can be vertically moved in the direction ofoptical axis O in a stable manner.

Furthermore, by disposing the pair of sensor magnets 342 a and 342 b atpositions which are point symmetrical about optical axis O, the effectof the magnetic interference from the pair of sensor magnets 342 a and342 b to the magnetic circuit (driving magnet 18, yoke 20) can beensured. As a result, it also is possible to reduce the transientresponse time of the vertical movement of the movable part in thedirection of optical axis O.

It is to be noted that the polarities of two plate-shaped driving magnetpieces 182 and the polarities of the pair of sensor magnets 342 a and342 b are not limited to the polarities illustrated in FIG. 3 and FIG.4, and may be opposite to each other. That is, plate-shaped drivingmagnet pieces 182 may be magnetized such that the inner periphery sideis magnetized to S pole, and the outer periphery side is magnetized to Npole, and, sensor magnets 342 a and 342 b may be magnetized such thatthe top surface side is magnetized to N pole, and the bottom surfaceside is magnetized to S pole.

It is to be noted that, as illustrated in FIG. 2 and FIG. 4, hole sensor344 is installed on flexible printed circuit (FPC) 40. As illustrated inFIG. 1 and FIG. 4, at front cutout part 202 a of yoke 20, flexibleprinted circuit (FPC) 40 is attached to the exterior wall of frontprotruding part 122 of base member 12 in a state where it is inserted inprotrusion part 207 of yoke 20. As illustrated in FIG. 1, flexibleprinted circuit (FPC) 40 is provided with a pair of cone-shapeddepressions 401 recessed inward at both end side portions thereof inhorizontal direction Y.

It is to be noted that the pair of sensor magnets 342 a and 342 b arerespectively housed in the pair of housing parts 140 a formed at lowerportions of the exterior walls opposite to each other in front-reardirection X with the Z axis (optical axis O) as the center incylindrical part 140 of lens holder 14 for the purpose of maintainingthe balance between the moving state and the stopping state of lensholder 14, achieving uniform weight disposition around the Z axis(optical axis O), and equalizing the magnetic interference force(resilience) with plate-shaped driving magnet piece 182. Accordingly,assuming that one sensor magnet 342 a and plate-shaped driving magnetpiece 182 are separated from each other by a certain distance and thatthe magnetic interference has no influence, the other sensor magnet 342b that is not opposite to hole sensor 344 can be replaced by a weighthaving a similar weight which is not magnetized.

Upper leaf spring (front spring) 22 is disposed on the upper side (frontside) of lens holder 14 in the direction of the optical axis O, andlower leaf spring (rear spring) 24 is disposed on the lower side (rearside) of lens holder 14 in the direction of optical axis O.

With reference to FIG. 5 to FIG. 7, the shapes of upper leaf spring 22and lower leaf spring 24 and their relationship are described.

FIG. 5 is a plan view illustrating a shape of upper leaf spring 22 asviewed from base member 12. FIG. 6 is a plan view illustrating a shapeof lower leaf spring 24 as viewed from base member 12. FIG. 7 is a planview illustrating a relationship between upper leaf spring 22 and lowerleaf spring 24.

First, with reference to FIG. 5, the shape of upper leaf spring 22 isdescribed.

Upper leaf spring 22 includes upper inner periphery end part 222 that isattached to an upper end portion of lens holder 14, and upper outerperiphery end part 224 that is attached to ring-shaped part 302 ofspacer 30. Four upper arm parts 226 are provided between upper innerperiphery end part 222 and upper outer periphery end part 224 along thecircumferential direction. Each upper arm part 226 connects upper innerperiphery end part 222 and upper outer periphery end part 224. Eachupper arm part 226 has a U-turn-shaped portion 226 a that is folded-backby 180 degrees.

Next, with reference to FIG. 6, the shape of lower leaf spring 24 isdescribed.

Lower leaf spring 24 includes lower inner periphery end part 242 that isattached to a lower end portion of lens holder 14, and lower outerperiphery end part 244 that is attached to actuator base (base member)12. Four lower arm parts 246 are provided between lower inner peripheryend part 242 and lower outer periphery end part 244 along thecircumferential direction. Each lower arm part 246 connects lower innerperiphery end part 242 and lower outer periphery end part 244. Eachlower arm part 246 has U-turn-shaped portion 246 a that is folded-backby 180 degrees.

Next, with reference to FIG. 7, the relationship between upper leafspring 22 and lower leaf spring 24 is described.

As illustrated in FIG. 7, four upper arm parts 226 of upper leaf spring22 and four lower arm parts 246 of lower leaf spring 24 havesubstantially the same shape in plan view.

Next, the way for feeding power to driving coil 16 is described.

As illustrated in FIG. 6, for the purpose of achieving power feeding todriving coil 16 through lower leaf spring 24, lower leaf spring 24 iscomposed of first and second spring pieces 24-1 and 24-2 that areelectrically isolated from each other. The shapes of first leaf springpiece 24-1 and second leaf spring piece 24-2 are substantiallyrotationally symmetrical about optical axis O of the lens.

First leaf spring piece 24-1 has first external connection terminal244-1 protruding forward from lower outer periphery end part 244. Secondleaf spring piece 24-2 has second external connection terminal 244-2protruding forward from lower outer periphery end part 244.

On the other hand, first leaf spring piece 24-1 has first terminal part242-1 protruding rearward from lower inner periphery end part 242.Second leaf spring piece 24-2 has second terminal part 242-2 protrudingforward from lower inner periphery end part 242. First terminal part242-1 is electrically connected to a first terminal end part (notillustrated) of driving coil 16 by soldering. Second terminal part 242-2is electrically connected to a second terminal end part (notillustrated) of driving coil 16 by soldering.

As illustrated in FIG. 1, first and second external connection terminals244-1 and 244-2 of lower leaf spring 24 are provided to protrude outwardfrom the pair of cone-shaped depressions 401 of flexible printed circuit(FPC) 40.

Accordingly, flexible printed circuit (FPC) 40 is electrically connectedwith the first terminal end part of driving coil 16 through firstexternal connection terminal 244-1 of lower leaf spring 24, and firstleaf spring piece 24-1 and first terminal part 242-1 of lower leafspring 24. Likewise, flexible printed circuit (FPC) 40 is electricallyconnected with the second terminal end part of driving coil 16 throughsecond external connection terminal 244-2 of lower leaf spring 24, andsecond leaf spring piece 24-2 and second terminal part 242-2 of lowerleaf spring 24.

In this manner, power is fed from flexible printed circuit (FPC) 40 todriving coil 16 through lower leaf spring 24.

When coil 16 is energized, a driving force in the direction of opticalaxis O is generated in lens holder 14 (lens barrel 11) with theinteraction between the magnetic field of driving magnet 18 and themagnetic field of the current flowing through driving coil 16, and thedriving force and the restoration force (biasing force) of the pair ofleaf springs 22 and 24 are balanced, whereby the position of lens holder14 (lens barrel 11) in the direction of optical axis O can be adjusted.

With reference to FIGS. 8A and 8B, the conductor pattern of the terminalpart formed in flexible printed circuit (FPC) 40 is described. FIG. 8Ais a front view of lens holder driving device 10, and FIG. 8Billustrates a relationship between seven terminals of the conductorpattern of flexible printed circuit (FPC) 40 and terminals which areconnected to the seven terminals.

As illustrated in FIG. 8A, flexible printed circuit (FPC) 40 includes,as the conductor pattern, first to seventh terminals Pin1 to Pin7 whichare disposed from the right side to the left side.

As illustrated in FIG. 8B, first terminal Pin1 is connected with ACTTerminal (+) that is first external connection terminal 244-1 of lowerleaf spring 24, second terminal Pin2 is connected with first outputterminal Hall output (?) of hole sensor 344, and third terminal Pin3 isconnected with first input terminal Hall input (+) of hole sensor 344.Fourth terminal Pin4 is connected with ground terminal GND. Fifthterminal Pin5 is connected with second output terminal Hall output (+)of hole sensor 344, sixth terminal Pin6 is connected with first inputterminal Hall input (?) of Hall device 344, and seventh terminal Pin7 isconnected with ACT Terminal (?) that is second external connectionterminal 244-2 of lower leaf spring 24.

Next, with reference to FIG. 9 to FIG. 12, details of the configurationof lower leaf spring 24 are described.

FIG. 9 and FIG. 10 are plan views of the assembly of lens holder drivingdevice 10 as viewed from base member 12. FIG. 9 illustrates a statebefore elastic adhesive agent 45 described later is provided (applied)to lower leaf spring 24, and FIG. 10 illustrates a state after elasticadhesive agents 45 is provided (applied) to lower leaf spring 24. FIG.11 is a partially enlarged view illustrating a part of FIG. 9 in anenlarged manner, and FIG. 12 is a partially enlarged view illustrating apart of FIG. 10 in an enlarged manner.

As illustrated in FIG. 10 and FIG. 12, lower leaf spring 24 is providedwith elastic adhesive agents 45 at U-turn-shaped portions 246 a of fourlower arm parts 246. Each elastic adhesive agent 45 is provided as abridge between opposite portions of U-turn-shaped portion 246 a. Fourelastic adhesive agents 45 are provided at equal angular intervals inthe circumferential direction around optical axis O.

It is to be noted that elastic adhesive agent 45 is composed of astretchable and flexible resin. In this example, as elastic adhesiveagent 45, a moisture-curable adhesive agent selected from amongsilicone-based adhesive agent and silyl group terminated polymer-basedadhesive agent is used.

As illustrated in FIG. 9 and FIG. 11, U-turn-shaped portions 246 a offour lower arm parts 246 have positioning protrusions 247 forfacilitating the bridging of elastic adhesive agent 45 with its surfacetension at the above-mentioned opposite portions (that is, the portionswhere elastic adhesive agent 45 is applied).

By applying elastic adhesive agent 45 at U-turn-shaped portions 246 a offour lower arm parts 246 in the above-mentioned manner, lens holderdriving device 10 according to the present embodiment suppresses thesecondary resonance (sub resonance) which is sway in the arrow directionof FIG. 12. In addition, elastic adhesive agent 45 is provided atU-turn-shaped portions 246 a of four lower arm parts 246, and thereforedoes not limit the original stroke of lens holder 14.

It is to be noted that elastic adhesive agent 45 can provide itsfunction with no problem even when washing solution is present.Accordingly, as usual, lens holder driving device 10 can be washed afterlens holder driving device 10 is assembled and the quality can bemaintained.

In addition, while stretchable and flexible resin is provided to lowerleaf spring 24 by applying elastic adhesive agent 45 in this example,the present invention is not limited to this. For example, thestretchable and flexible resin may be provided to lower leaf spring 24by bonding an elasticity sheet of such a stretchable and flexible resinto lower leaf spring 24 with a double-sided tape. Alternatively, thestretchable and flexible resin may be provided to lower leaf spring 24by molding lower leaf spring 24 and stretchable and flexible resin intwo colors by outsert molding. Further, stretchable and flexible resinmay also be provided to lower leaf spring 24 by UV curing a photoresist.In addition, the place where the stretchable and flexible resin isprovided is not limited to lower leaf spring 24, and it is alsoeffective to provide the stretchable and flexible resin at upper leafspring 22 or both of leaf springs 22 and 24.

Next, with reference to FIG. 13 to FIG. 16, front cutout part (firstcutout part) 202 a and rear cutout part (second cutout part) 202 bformed in yoke 20 are described.

FIG. 13 is a front view of lens holder driving device 10, and FIG. 14 isa back view of lens holder driving device 10. FIG. 15 is a perspectiveview of yoke 20, and FIG. 16 is a front view of yoke 20.

Front plate part (first plate part) 202F of yoke 20 has front cutoutpart (first cutout part) 202 a having a trapezoidal shape, and likewise,rear plate part (second plate part) 202B has rear cutout part (secondcutout part) 202 b having a trapezoidal shape.

By employing yoke 20 of the above-mentioned structure, the pair ofsensor magnets 342 a and 342 b (see FIG. 2) is prevented from beingnegatively influenced by the magnetic field generated by a magneticcircuit composed of yoke 20 and driving magnet 18. In other words, theinfluence of magnetic field of the above-mentioned magnetic circuit onthe pair of sensor magnets 342 a and 342 b can be equalized, and,reduced as much as possible. As a result, it is possible to suppress thenon-uniformity of the thrust by the stroke amount of the movable part(lens barrel 11 and lens holder 14).

Next, with reference to FIG. 17 to FIG. 21, a structure in which basemember 12 and yoke 20 are fitted together through spacer (inner housing)30 is described.

FIG. 17 is a perspective view illustrating an assembly in which spacer(inner housing) 30, driving magnet 18 and upper leaf spring 22 areinstalled in yoke 20. FIG. 18 is a perspective view illustrating anassembly in which upper leaf spring 22 is installed to spacer (innerhousing) 30. FIG. 19 is a longitudinal sectional view taken along theline IV-IV of FIG. 1. FIG. 20 is a cross-sectional perspective viewspecifically illustrating a part (front side) of the cross-section ofFIG. 19, and FIG. 21 is a cross-sectional perspective view specificallyillustrating a part (rear side) of the cross-section of FIG. 19.

After upper leaf spring 22 is mounted on spacer (inner housing) 30 asillustrated in FIG. 18, spacer (inner housing) 30 is installed along theinner wall of yoke 20 as illustrated in FIG. 17.

In addition, as illustrated in FIG. 19, spacer (inner housing) 30 isfitted with base member 12. At this time, as illustrated in FIG. 20, ina region around front cutout part (first cutout part) 202 a of yoke 20,front protruding part (first protruding part) 122 of base member 12 andfront U-shaped plate part (first U-shaped plate part) 305 of spacer(inner housing) 30 are engaged with each other (in engagement). Inaddition, as illustrated in FIG. 21, in a region around rear cutout part(second cutout part) 202 b of yoke 20, rear protruding part (secondprotruding part) 123 of base member 12 and rear U-shaped plate part(second U-shaped plate part) 306 of spacer (inner housing) 30 areengaged with each other (in engagement).

In addition, by supplying adhesive resin (adhesive agent) by utilizingcapillarity to the above-mentioned engaging portion (engagementportion), the gap of the above-mentioned engaging portion (engagementportion) is closed. In this manner, it is possible to prevent dusts andforeign matters from intruding into lens holder driving device 10 fromthe outside through the gap.

Thus, the combination of first protruding part 122, second protrudingpart 123, and inner housing 30 serves as a foreign matter intrusionprevention member that prevents foreign matters from intruding into theinside from first and second cutout parts 202 a and 202 b of first andsecond plate parts 202F and 202B.

Next, with reference to FIG. 22, a state where hole sensor (magneticdetection device) 344 is attached on base member 12 is described.

FIG. 22 is a perspective view illustrating lens holder driving device 10illustrated in FIG. 1 in which flexible printed circuit (FPC) 40 isomitted.

As illustrated in FIG. 2 and FIG. 22, hole sensor 344 is inserted torectangular hole 122 a formed in front protruding part (first protrudingpart) 122 of base member 12. In this manner, the position of hole sensor344 is set. In addition, in front protruding part 122 of base member 12,C plane 122 b is provided around rectangular hole 122 a. Resin such asepoxy resin (adhesive agent) is applied to C plane 122 b to close thegap between hole sensor 344 and rectangular hole 122 a, and thus lensholder driving device 10 has an enclosed structure.

With this structure, the position of hole sensor 344 is stabilized at aposition, and non-uniformity of the output of hole sensor 344 can besuppressed. In addition, since resin (adhesive agent) is supplied intothe gap between hole sensor 344 and base member 12, rectangular hole 122a is closed. As a result, it is possible to prevent intrusion of foreignmatters and the like through rectangular hole 122 a.

With reference to FIG. 23A to FIG. 24B, a configuration of flexibleprinted circuit (FPC) 40 is described.

FIG. 23A to FIG. 23C are a front view, a rear view, and a plan view (topview) of flexible printed circuit (FPC) 40, respectively. FIG. 24A andFIG. 24B are a front view and a rear view of base material 402 offlexible printed circuit (FPC) 40, respectively.

Flexible printed circuit (FPC) 40 is composed of base material 402,first cover film 404, and second cover film 406.

As illustrated in FIG. 24A, first conductor pattern 402 a is formed onthe main surface of base material 402. First conductor pattern 402 aincludes grounding pattern 402 ag at a center portion thereof. Asillustrated in FIG. 24B, second conductor pattern 402 b is formed on therear surface of base material 402. Second conductor pattern 402 b isintended for connection of the four terminals of hole sensor 344. In theexample illustrated in the drawing, first and second conductor patterns402 a and 402 b are composed of a Cu pattern.

As illustrated in FIG. 23A, first cover film 404 is bonded on the mainsurface of base material 402 so as to cover a part of first conductorpattern 402 a. First cover film 404 is composed of a black cover film(light shielding film) that blocks light.

As illustrated in FIG. 23B, second cover film 406 is bonded on the rearsurface of base material 402 so as to cover a part of second conductorpattern 402 b.

With reference FIG. 25A to FIG. 25E, a state where hole sensor 344 isinstalled on flexible printed circuit (FPC) 40 is described. FIG. 25A toFIG. 25E are a front view of, a rear view, a plan view (top view), aperspective view as viewed from the front surface side, and aperspective view as viewed from the back side of the state where holesensor 344 is installed on flexible printed circuit (FPC) 40,respectively.

As illustrated in FIG. 25B and FIG. 25E, hole sensor 344 is joined tosecond conductor pattern 402 b by soldering on the rear surface (backsurface) side of flexible printed circuit (FPC) 40.

Accordingly, as illustrated in FIG. 25A and FIG. 25D, black cover film(light shielding film) 404 is bonded on the main surface of flexibleprinted circuit (FPC) 40 which is opposite to the rear surface on whichhole sensor 344 is attached. In this manner, it is possible to preventintrusion of light (stray light) into lens holder driving device 10through the gap between hole sensor 344 and rectangular hole 122 a (seeFIG. 2) of base member 12.

Next, with reference to FIG. 26 to FIG. 28, electric connection offlexible printed circuit (FPC) 40, yoke 20, and first and secondexternal connection terminals 244-1 and 244-2 of lower leaf spring 24 isdescribed.

FIG. 26 is a plan view of lens holder driving device 10 illustrating aconnection state of flexible printed circuit (FPC) 40. FIG. 27 is apartially enlarged perspective cross-sectional view illustrating aregion around cone-shaped depression 401 of flexible printed circuit(FPC) 40 of FIG. 26 in an enlarged manner. FIG. 28 is a partiallyenlarged perspective view illustrating a region around protrusion part207 of yoke 20 of FIG. 26 in an enlarged manner.

As described above, flexible printed circuit (FPC) 40 is provided with apair of cone-shaped depressions 401 at both end portions in horizontaldirection (first direction) Y. In addition, first and second externalconnection terminals 244-1 and 244-2 of lower leaf spring 24 areprovided to protrude outward from the pair of cone-shaped depressions401 of flexible printed board (FPC) 40. Here, first and second externalconnection terminals 244-1 and 244-2 of lower leaf spring 24 (see FIG.6) protrude in the pair of cone-shaped depressions 401 withoutprotruding over the main surface of flexible printed circuit (FPC) 40.

As illustrated in FIG. 26 and FIG. 27, first and second externalconnection terminals 244-1 and 244-2 (see FIG. 6) of lower leaf spring24 are joined to the pair of cone-shaped depressions 401 of flexibleprinted circuit (FPC) 40 with solder 52. Thus, a large joint area can beachieved.

In addition, as described above, flexible printed circuit (FPC) 40 isattached on the exterior wall of front protruding part (first protrudingpart) 122 of base member 12 at front cutout part (first cutout part) 202a of yoke 20 in a state where it is inserted to protrusion part 207 ofyoke 20. Protrusion part 207 is Sn-plated.

As illustrated in FIG. 26 and FIG. 28, at protrusion part 207, yoke 20and grounding pattern 402 ag of flexible printed circuit (FPC) 40 arejoined together with solder 54 so as to be conductive.

With this structure, the resistance value of grounding pattern 402 agcan be suppressed to a minimum value, and peel-off of flexible printedcircuit (FPC) 40 can be prevented.

In addition, as illustrated in FIG. 28, a part of protrusion part 207 ofyoke 20 is half-punched.

Accordingly, flexible printed circuit (FPC) 40 is coupled with basemember 12 and spacer (inner housing) 30 with solders 52 and 54 at threepositions. As a result, the strength of flexible printed circuit (FPC)40 can be reinforced. In this manner, peel-off of flexible printedcircuit (FPC) 40 can be prevented. In addition, since protrusion part207 of yoke 20 is half-punched, projecting of solder 54 can besuppressed.

Next, with reference to FIG. 29 and FIG. 30, an abutting structurebetween upper leaf spring 22 and ring-shaped upper end part 204 of yoke20 is described.

FIG. 29 is a perspective view of lens holder driving device 10. FIG. 30is a partially enlarged view illustrating an abutting portion betweenupper leaf spring 22 and ring-shaped upper end part 204 of yoke 20 ofFIG. 29 in an enlarged manner.

As illustrated in FIG. 29, ring-shaped upper end part 204 of yoke 20 ofFIG. 29 includes semi-punched portions 204 a that are semi-punched ateight portions on the inner periphery side.

When lens holder 14 is moved (driven) upward, upper leaf spring 22 islocked by eight semi-punched portions 204 a (brought into contact withsemi-punched portions 204 a). That is, eight semi-punched portions 204 aof yoke 20 act as an upper side stopper (lock member) that limits theupward movement of lens holder 14.

Since a plurality of semi-punched portions 204 a are formed atring-shaped upper end part 204 of yoke 20, the strength of yoke 20 canbe increased. As a result, even when a camera-equipped mobile terminalhaving lens holder driving device 10 is mistakenly dropped and themovable part (lens barrel 11 and lens holder 14) is brought into contactwith yoke 20, it is possible to suppress deformation of yoke 20. At thetime of the contact, upper leaf spring 22 makes contact with the bottomsurfaces of semi-punched portions 204 a of yoke 20. That is, the contactis made between metals, and therefore it is possible to suppressdeformation of lens holder 14 as a molded article.

With reference to FIG. 31 and FIG. 32, a configuration of spacer (innerhousing) 30 is described in more detail.

FIG. 31 is a perspective view of spacer (inner housing) 30. FIG. 32 is apartially enlarged view illustrating a part of FIG. 31 in an enlargedmanner.

As illustrated in FIG. 31, each of four vertical extending parts 304provided at four corners of spacer (inner housing) 30 has twoprotrusions 3042 that protrude outward in the radial direction (in FIG.31, only four protrusions 3042 are illustrated). That is, spacer (innerhousing) 30 has eight protrusions 3042 in total.

As illustrated in FIG. 32, each protrusion 3042 has a substantially halfcolumnar shape extending in vertical direction Z (extending in adirection parallel to the direction of optical axis O). Each protrusion3042 has top end portion 3042 a having a substantially half cone shapeat an upper part thereof.

Since eight protrusions 3042 are provided at four corners of spacer(inner housing) 30 in the above-mentioned manner, the position of yoke20 can be accurately set. To be more specific, when yoke 20 is disposedto cover spacer (inner housing) 30, the inner wall of outer cylinderpart 202 of yoke 20 is guided by end portions 3042 a having asubstantially half cone shape, and pushes down eight protrusions 3042 ofspacer (inner housing) 30, and consequently, yoke 20 and spacer (innerhousing) 30 are fitted to each other in a lightly pressed state. As aresult, rattle of yoke 20 can be prevented.

With this configuration, shift of the central axis of yoke 20 withrespect to optical axis O of the lens can be adjusted. As a result, itis possible to equalize the influence of the interference of themagnetism generated from the magnetic circuit composed of driving magnet18 and yoke 20 on the pair of sensor magnets 342. This also makes itpossible to limit the level of the sub resonance of lens holder drivingdevice 10 to a small level.

Lens holder driving device 10 according to the first embodiment controlsthe position of lens holder 14 in the direction of optical axis O byfeedback control as described next.

First, a driving current is supplied to driving coil 16 to move lensholder 14 in the direction of optical axis O, and the position of lensholder 14 in the direction of optical axis O (detection position) andthe detection value detected at hole sensor 344 of position detectionpart 34 are measured. In this manner, the relationship of the drivingcurrent, the detection position, and the detection value is determined.The driving current and the detection position correspond to each otherin one-to-one relationship. Accordingly, when moving lens holder 14 to adesired target position (a position in the direction of optical axis O),it suffices to supply driving coil 16 with a driving currentcorresponding to the target position.

To achieve conversion of a detection value into a detection position,the relationship between the detection value and the detection position(one-to-one relationship) is stored in a ROM (read-only memory).Accordingly, the ROM serves as a conversion part that converts adetection value into a detection position.

A control part (not illustrated) for achieving feedback controldetermines a driving current required for moving lens holder 14 to atarget position on the basis of an image signal of the imaging deviceand a detection value detected by hole sensor 344, and supplies thedetermined driving current to driving coil 16.

The control part includes the above-mentioned conversion part (ROM), atarget position calculation part, a comparison part, and an operationpart. The target position calculation part calculates a target position(focusing position) of lens holder 14 based on an image signal of theimaging device. Here, the focusing position is a position of lens holder14 where the contrast value of a captured image obtained by processingof an image signal is optimized. The comparison part compares the targetposition and the detection position, and outputs a control deviation.The operation part supplies an operation amount at which the controldeviation is zero as a driving current to driving coil 16.

By performing feedback control in the above-mentioned manner, lensholder 14 can be stopped at a target position (focusing position) in thedirection of optical axis O in a short time of 10 milliseconds to 20milliseconds, for example.

FIG. 33 is a perspective view illustrating camera-equipped mobileterminal 80 in which lens holder driving device 10 is installed.Camera-equipped mobile terminal 80 illustrated in the drawing iscomposed of a smartphone. Lens holder driving device 10 is attached at apredetermined position of camera-equipped mobile terminal 80. With thisstructure, the user can capture an image by using camera-equipped mobileterminal 80.

While camera-equipped mobile terminal 80 is composed of a smartphone inthis example, the camera-equipped mobile terminal may be acamera-equipped mobile phone, a note-type personal computer, atablet-type personal computer, a mobile game machine, a Web camera, oran in-vehicle camera.

Second Embodiment

With reference to FIGS. 34 and 35, lens holder driving device 10Aaccording to a second embodiment of the present invention is described.

FIG. 34 is a perspective view of lens holder driving device 10A in whichyoke 20, upper leaf spring 22, and spacer (inner housing) 30 areomitted. FIG. 35 is a plan view of lens holder driving device 10Aillustrated in FIG. 34.

Here, as illustrated in FIG. 34 and FIG. 35, an orthogonal coordinatesystem (X, Y, Z) is used. In the orthogonal coordinate system (X, Y, Z)of FIG. 34 and FIG. 35, the X-axis direction is the front-rear direction(depth direction), the Y-axis direction is the horizontal direction(width direction), and the Z-axis direction is the vertical direction(height direction). In addition, in the example illustrated in FIG. 34and FIG. 35, vertical direction Z is the direction of optical axis O ofthe lens. It is to be noted that, in the present embodiment, the Y-axisdirection (horizontal direction) is also referred to as first direction,and the X-axis direction (front-rear direction) is also referred to assecond direction.

It should be noted that, when actually used, the direction of opticalaxis O, that is, the Z-axis direction is the front-rear direction. Inother words, the upward direction of the

Z axis is the forward direction, and the downward direction of the Zaxis is the rearward direction.

Lens holder driving device 10A illustrated in the drawing is used in amobile terminal capable of performing auto focus (AF) such as acamera-equipped mobile phone, a smartphone illustrated in FIG. 33, anote-type personal computer, a tablet-type personal computer, a mobilegame machine, a Web camera, and an in-vehicle camera.

Except for the following difference of the driving magnet, lens holderdriving device 10A illustrated in the drawing has a configurationidentical to that of lens holder driving device 10 illustrated in FIG. 1to FIG. 4, and operates similarly to lens holder driving device 10illustrated in FIG. 1 to FIG. 4. Accordingly, the driving magnet isdenoted with reference numeral 18A. Components having functions similarto those of the components of lens holder driving device 10 illustratedin FIG. 1 to FIG. 4 are denoted with the same reference numerals, andthe description thereof will be omitted for simplification.

As with driving magnet 18 according to the first embodiment, drivingmagnet 18A is composed of two plate-shaped driving magnet pieces 182A;however, the shape of driving magnet 18A is different from that ofplate-shaped driving magnet piece 182 of driving magnet 18.

Specifically, each of two plate-shaped driving magnet pieces 182A has,at both end portions thereof, protrusion part 182Aa having asubstantially triangular prism shape that are disposed to be opposite tofour short side parts 164 of driving coil 16 at four corners of yoke 20(see FIG. 2). The inner periphery side of each protrusion part 182Aa hasa planar shape. Accordingly, plate-shaped driving magnet piece 182A canbe readily manufactured.

Lens holder driving device 10A according to the second embodiment canachieve an effect similar to that of lens holder driving device 10according to the first embodiment, and in addition, can achieve aneffect described next.

Specifically, since each of two plate-shaped driving magnet pieces 182Ahas protrusion part 182Aa having a substantially triangular prism shapeat both end portions thereof, the thrust of the driving mechanismaccording to the second embodiment can be advantageously increased incomparison with the driving mechanism according to the first embodiment.

Third Embodiment

With reference to FIG. 36 and FIG. 37, lens holder driving device 10Baccording to a third embodiment of the present invention is described.

FIG. 36 is a perspective view of lens holder driving device 10B in whichyoke 20, upper leaf spring 22, and spacer (inner housing) 30 areomitted. FIG. 37 is a plan view of lens holder driving device 10Billustrated in FIG. 36.

Here, as illustrated in FIG. 36 and FIG. 37, an orthogonal coordinatesystem (X, Y, Z) is used. In the orthogonal coordinate system (X, Y, Z)of FIG. 36 and FIG. 37, the X-axis direction is the front-rear direction(depth direction), the Y-axis direction is the horizontal direction(width direction), and the Z-axis direction is the vertical direction(height direction). In addition, in the example illustrated in FIG. 36and FIG. 37, vertical direction Z is the direction of optical axis O ofthe lens. It is to be noted that, in the present embodiment, the Y-axisdirection (horizontal direction) is also referred to as first direction,and the X-axis direction (front-rear direction) is also referred to assecond direction.

It should be noted that, when actually used, the direction of opticalaxis O, that is, the Z-axis direction is the front-rear direction. Inother words, the upward direction of the Z axis is the forwarddirection, and the downward direction of the Z axis is the rearwarddirection.

Lens holder driving device 10B illustrated in the drawing is used in amobile terminal capable of performing auto focus (AF) such as acamera-equipped mobile phone, a smartphone illustrated in FIG. 33, anote-type personal computer, a tablet-type personal computer, a mobilegame machine, a Web camera, and an in-vehicle camera.

Except for the following difference of the driving magnet describedlater, lens holder driving device 10B illustrated in the drawing has aconfiguration identical to that of lens holder driving device 10illustrated in FIG. 1 to FIG. 4, and operates similarly to lens holderdriving device 10 illustrated in FIG. 1 to FIG. 4. Components havingfunctions similar to those of the components of lens holder drivingdevice 10 illustrated in FIG. 1 to FIG. 4 are denoted with the samereference numerals, and the description thereof will be omitted forsimplification.

Driving magnet 18B further includes four driving magnet pieces 184having a substantially triangular prism shape which are respectivelyopposite to four short side parts 164 of driving coil 16 at four cornersof the yoke in addition to two plate-shaped driving magnet pieces 182.The inner periphery side of each driving magnet piece 184 has a planarshape. Accordingly, driving magnet piece 184 can be readilymanufactured.

Lens holder driving device 10B according to the third embodiment canachieve an effect similar to that of lens holder driving device 10according to the first embodiment, and in addition, can achieve aneffect described next.

That is, since driving magnet 18 includes not only two plate-shapeddriving magnet pieces 182, but also four driving magnet pieces 184having a substantially triangular prism shape, the thrust of the drivingmechanism according to the third embodiment can be advantageouslyincreased in comparison with the driving mechanism according to thefirst embodiment.

An exemplary mode of the present invention is described below.

In the exemplary mode of the present invention, a lens holder drivingdevice (10; 10A; 10B) includes: a lens holder (14) to which a lensbarrel (11) is attachable; a fixing part (12, 30) disposed at an outerperiphery of the lens holder (14); a driving mechanism (16, 18; 18A;18B, 20) for driving the lens holder (14) in a direction of an opticalaxis (O) of a lens; and a position detection part (34) configured todetect a position of the lens holder (14) in the direction of theoptical axis (O). The fixing part includes a base member (12) disposedon a lower side of the lens holder (14). The driving mechanism includesa yoke (20) uprightly provided on the base member (12). The positiondetection part includes a sensor magnet (342 a) attached on acorresponding outer peripheral surface of the lens holder (14) in adirection (X) orthogonal to the optical axis (O), and a magneticdetection device (344) provided to the fixing part such that themagnetic detection device (344) is opposite to the sensor magnet (342a). The yoke (20) includes an outer cylinder part (202) having acylindrical shape, and the outer cylinder part (202) includes aplurality of plate parts (202F, 202B) which are opposite to each otherin the direction (X) orthogonal to the optical axis (O), the plate parts(202F, 292B) having cutout parts (202 a, 202 b) at positions opposite tothe sensor magnet (342 a). The lens holder driving device (10; 10A; 10B)includes a foreign matter intrusion prevention member (122, 123, 30)configured to prevent intrusion of foreign matters from the cutout part(202 a, 202 b) of the plate part (202F, 202B).

In the lens holder driving device (10; 10A; 10B), the lens holderdriving device (10; 10A; 10B) may further include an upper leaf spring(22) configured to couple the lens holder (14) and the fixing part (12,30) at an upper part thereof, and a lower leaf spring (24) configured tocouple the lens holder (14) and the fixing part (12, 30) at a lower partthereof.

The position detection part (34) may be provided in a region around thelower leaf spring (24). The yoke (20) may have a substantiallyquadrangular cylindrical shape. Preferably, the driving mechanism mayfurther include a driving coil (16) fixed at a periphery of the lensholder (14) in a region on a side closer to the upper leaf spring (22),and a driving magnet (18; 18A; 18B) including plate-shaped drivingmagnet pieces (182; 182A) which are disposed at a pair of inner wallsurfaces of the yoke (20) opposite to each other in a first direction(Y) orthogonal to the direction of the optical axis (O), theplate-shaped driving magnet pieces (182; 182A) being respectivelydisposed to be opposite to the driving coil (16). The base member (12)may include a ring-shaped base part (120), and first and secondprotruding parts (122, 123) which are opposite to each other in a seconddirection

(X) orthogonal to the direction of the optical axis (O) and the firstdirection (Y) and protrude upward from the base part (120), the firstprotruding part (122) having a rectangular hole (122 a). The positiondetection part may include a sensor magnet (342 b) as one of a pair ofsensor magnets (342 a, 342 b) attached on corresponding outer peripheralsurfaces of the lens holder (14) in the second direction (X), and themagnetic detection device (344) that is inserted to the rectangular hole(122 a) of the first protruding part (122) of the base member (12), andfirmly fixed with resin, the magnetic detection device (344) beingopposite to the sensor magnet (342 a). The outer periphery part (202) ofthe yoke (20) has a substantially square cylindrical shape. The yoke(20) may further include a ring-shaped upper end part (204) having asubstantially quadrangular shape protruding inward at an upper end ofthe outer cylinder part (202), and an inner vertical extending part(206) extending perpendicularly downward in a direction parallel to theoptical axis (O) at four corners of an inside of the ring-shaped upperend part. The outer cylinder part (202) may include first and secondplate parts (202F, 202B) that are opposite to each other in the seconddirection (X) as the plurality of plate parts, the first and secondplate parts (202F, 202B) respectively having first and second cutoutparts (202 a, 202 b) that open downward at positions opposite to thepair of sensor magnets (342 a, 342 b) as the cutout part. The fixingpart may further include an inner housing (30) provided such that theinner housing (30) is sandwiched between the base member (12) and theyoke (20) and housed in an inner wall surface of the yoke (20). In thiscase, a combination of the first protruding part (122), the secondprotruding part (123), and the inner housing (30) functions as theforeign matter intrusion prevention member.

Desirably, the inner housing (30) includes a ring-shaped part (302)provided at an upper part of an inner wall surface of the outer cylinderpart (202) of the yoke (20), a vertical extending part (304)perpendicularly extending downward from four corners of the ring-shapedpart (302) in a direction parallel to the optical axis (O), and firstand second

U-shaped plate parts (305, 306) extending downward in a directionparallel to the optical axis (O) from a pair of sides of the ring-shapedpart (302) which are opposite to each other in the second direction (X).In this case, the first protruding part (122) of the base member (12)and the first U-shaped plate part (305) of the inner housing (30) arefitted to each other in a region around the first cutout part (202 a) ofthe first plate part (202F). In addition, the second protruding part(123) of the base member (12) and the second U-shaped plate part (306)of the inner housing (30) are fitted to each other in a region aroundthe second cutout part (202 b) of the second plate part (202B).

In the lens holder driving device (10; 10A; 10B), the lens holderdriving device (10; 10A; 10B), preferably, the plate-shaped drivingmagnet pieces (182; 182A) and the pair of sensor magnets (342 a, 342 b)are disposed at positions which are point symmetrical about the opticalaxis (O).

The lens holder driving device (10; 10A; 10B) may further include aflexible printed circuit (40) attached on an exterior wall of the firstprotruding part (122) of the base member (12) at the first cutout part(202 a) of the first plate part (202F). In this case, preferably, themagnetic detection device (344) is attached on an internal surface sideof the flexible printed circuit (40); and the flexible printed circuit(40) includes a light shielding film (404) configured to cover at leasta portion which is opposite to the magnetic detection device (344) on anexternal surface side of the flexible printed circuit (40). The flexibleprinted circuit (40) may include a pair of cone-shaped depressions (401)that are recessed inward at both end portions in the first direction(Y). In this case, a pair of external connection terminals (244-1,244-2) of the lower leaf spring (24) protrude and joined thereto bysoldering in a state where the external connection terminals (244-1,244-2) are housed in the pair of cone-shaped depressions (401) withoutprotruding over a main surface of the flexible printed circuit (40). Theflexible printed circuit (40) may have a grounding pattern (402 ag) at acenter portion on the external surface side thereof. In this case,preferably, the first plate part (202F) of the yoke (20) has aprotrusion part (207) protruding downward at the first cutout part (202a); the flexible printed circuit (40) is attached on an exterior wall ofthe first protruding part (122) of the base member (12) in a state wherethe flexible printed circuit (40) is inserted in the protrusion part(207); and the yoke (20) and the grounding pattern (402 ag) are joinedtogether by soldering at the protrusion part (207). Preferably, theprotrusion part (207) is Sn-plated and half-punched.

In the lens holder driving device (10; 10A; 10B), preferably, thering-shaped upper end part (204) of the yoke (20) includes asemi-punched portion (204 a) that is semi-punched at a plurality ofportions on an inner periphery side of the ring-shaped upper end part(204). In this case, the upper leaf spring (22) makes contact with theplurality of semi-punched portions (204 a) when the lens holder (14)moves upward.

In the lens holder driving device (10; 10A; 10B), preferably, thevertical extending part (304) of the inner housing (30) has a protrusion(3042) protruding outward in a radial direction. In this case, the yoke(20) is fitted to the inner housing (30) in a lightly pressed state withthe outer cylinder part (202) of the yoke (20) pushing down theprotrusion (3042) of the inner housing (30) to thereby set a position ofthe yoke (20) with respect to the inner housing (30). Desirably, theprotrusion (3042) has a substantially semi-columnar shape which extendsin a direction parallel to the direction of the optical axis (O).Desirably, the protrusion (3042) has a top end portion (3042 a) having asubstantially half cone shape at an upper part thereof.

According to a second exemplary mode of the present invention, acamera-equipped mobile terminal (80) in which the above-mentioned lensholder driving device (10; 10A; 10B) is installed can be obtained.

It is to be noted that the reference numerals in parentheses are merelyexamples intended for convenience of description of the presentinvention, and the present invention is not limited thereto.

While the invention made by the present inventor has been specificallydescribed based on the preferred embodiments, it is not intended tolimit the present invention to the above-mentioned preferred embodimentsbut the present invention may be further modified within the scope andspirit of the invention defined by the appended claims.

This application is entitled to and claims the benefit of JapanesePatent Application No. 2014-160592 filed on Aug. 6, 2014, the disclosureeach of which including the specification, drawings and abstract isincorporated herein by reference in its entirety.

REFERENCE SIGNS LIST

-   10, 10A, 10B Lens holder driving device-   11 Lens barrel-   12 Base member (actuator base)-   120 Base part-   122 Front protruding part (first protruding part)-   122 a Rectangular hole-   122 b C plane-   123 Rear protruding part (second protruding part)-   14 Lens holder-   140 Cylindrical part-   140 a Housing part-   16 Driving coil-   162 Long side part-   164 Short side part-   18, 18A, 18B Driving magnet-   182, 182A Plate-shaped driving magnet piece-   182Aa Substantially triangular prism shape protrusion part-   184 Substantially triangular prism shape driving magnet piece-   20 Yoke-   202 Outer cylinder part-   202 a Front cutout part (first cutout part)-   202 b Rear cutout part (second cutout part)-   202F Front plate part (first plate part)-   202B Rear plate part (second plate part)-   202L Left plate part-   202R Right plate part-   204 Ring-shaped upper end part-   204 a Semi-punched portion-   206 Inner vertical extending part-   207 Protrusion part-   22 Upper leaf spring-   222 Upper inner periphery end part-   224 Upper outer periphery end part-   226 Upper arm part-   226 a U-turn-shaped portion-   24 Lower leaf spring-   24-1 First spring piece-   24-2 Second spring piece-   242 Lower inner periphery end part-   242-1 First terminal part-   242-2 Second terminal part-   244 Lower outer periphery end part-   244-1 First external connection terminal-   244-2 Second external connection terminal-   246 Lower arm part-   246 a U-turn-shaped portion-   247 Positioning protrusion-   30 Spacer (inner housing)-   302 Ring-shaped part-   30 Four vertical extending parts-   304 Two protrusions-   3042 a Top end portion-   305 Front U-shaped plate part (first U-shaped plate part)-   306 Rear U-shaped plate part (second U-shaped plate part)-   34 Position detection part-   342 a Sensor magnet-   342 b Sensor magnet-   344 Hole sensor (magnetic detection device)-   40 Flexible printed circuit (FPC)-   401 Cone-shaped depression-   402 Base material-   402 a First conductor pattern-   402 ag Grounding pattern-   402 b Second conductor pattern-   404 First cover film (light shielding film)-   406 Second cover film-   45 Elastic adhesive agent (stretchable and flexible resin)-   52, 54 Solder-   80 Camera-equipped mobile terminal (smartphone)-   O Optical axis-   X Front-rear direction (second direction)-   Y Horizontal direction (first direction)-   Z Vertical direction

1. A lens holder driving device comprising: a lens holder to which alens barrel is attachable; a fixing part disposed at an outer peripheryof the lens holder; a driving mechanism for driving the lens holder in adirection of an optical axis (O) of a lens; and a position detectionpart configured to detect a position of the lens holder in the directionof the optical axis (O), wherein: the fixing part includes a base memberdisposed on a lower side of the lens holder; the driving mechanismincludes a yoke uprightly provided on the base member; the positiondetection part includes: a sensor magnet attached on a correspondingouter peripheral surface of the lens holder in a direction (X)orthogonal to the optical axis (O), and a magnetic detection deviceprovided to the fixing part such that the magnetic detection device isopposite to the sensor magnet; the yoke includes an outer cylinder parthaving a cylindrical shape; the outer cylinder part includes a pluralityof plate parts which are opposite to each other in the direction (X)orthogonal to the optical axis (O), the plate parts having cutout partsat positions opposite to the sensor magnet; and the lens holder drivingdevice includes a foreign matter intrusion prevention member configuredto prevent intrusion of foreign matters from the cutout part of theplate part.
 2. The lens holder driving device according to claim 1,wherein: the lens holder driving device further includes: an upper leafspring configured to couple the lens holder and the fixing part at anupper part thereof, and a lower leaf spring configured to couple thelens holder and the fixing part at a lower part thereof; the positiondetection part is provided in a region around the lower leaf spring; theyoke has a substantially quadrangular cylindrical shape; the drivingmechanism further includes: a driving coil fixed at a periphery of thelens holder in a region on a side closer to the upper leaf spring, and adriving magnet including plate-shaped driving magnet pieces which aredisposed at a pair of inner wall surfaces of the yoke opposite to eachother in a first direction (Y) orthogonal to the direction of theoptical axis (O), the plate-shaped driving magnet pieces beingrespectively disposed to be opposite to the driving coil; the basemember includes: a ring-shaped base part, and first and secondprotruding parts which are opposite to each other in a second direction(X) orthogonal to the direction of the optical axis (O) and the firstdirection (Y) and protrude upward from the base part, the firstprotruding part having a rectangular hole; the position detection partincludes: a sensor magnet as one of a pair of sensor magnets attached oncorresponding outer peripheral surfaces of the lens holder in the seconddirection (X), and the magnetic detection device that is inserted to therectangular hole of the first protruding part of the base member, andfirmly fixed with resin, the magnetic detection device being opposite tothe sensor magnet; the outer periphery part of the yoke has asubstantially square cylindrical shape; the yoke further includes: aring-shaped upper end part having a substantially quadrangular shapeprotruding inward at an upper end of the outer cylinder part, and aninner vertical extending part extending perpendicularly downward in adirection parallel to the optical axis (O) at four corners of an insideof the ring-shaped upper end part; the outer cylinder part includesfirst and second plate parts that are opposite to each other in thesecond direction (X) as the plurality of plate parts, the first andsecond plate parts respectively having first and second cutout partsthat open downward at positions opposite to the pair of sensor magnetsas the cutout part; the fixing part further includes an inner housingprovided such that the inner housing is sandwiched between the basemember and the yoke and housed in an inner wall surface of the yoke; anda combination of the first protruding part, the second protruding part,and the inner housing functions as the foreign matter intrusionprevention member.
 3. The lens holder driving device according to claim2, wherein: the inner housing includes: a ring-shaped part provided atan upper part of an inner wall surface of the outer cylinder part of theyoke, a vertical extending part perpendicularly extending downward fromfour corners of the ring-shaped part in a direction parallel to theoptical axis (O), and first and second U-shaped plate parts extendingdownward in a direction parallel to the optical axis (O) from a pair ofsides of the ring-shaped part which are opposite to each other in thesecond direction (X); the first protruding part of the base member andthe first U-shaped plate part of the inner housing are fitted to eachother in a region around the first cutout part of the first plate part;and the second protruding part of the base member and the secondU-shaped plate part of the inner housing are fitted to each other in aregion around the second cutout part of the second plate part.
 4. Thelens holder driving device according to claim 3, wherein theplate-shaped driving magnet pieces and the pair of sensor magnets aredisposed at positions which are point symmetrical about the optical axis(O).
 5. The lens holder driving device according to claim 4 furthercomprising: a flexible printed circuit attached on an exterior wall ofthe first protruding part of the base member at the first cutout part ofthe first plate part, wherein: the magnetic detection device is attachedon an internal surface side of the flexible printed circuit; and theflexible printed circuit includes a light shielding film configured tocover at least a portion which is opposite to the magnetic detectiondevice on an external surface side of the flexible printed circuit. 6.The lens holder driving device according to claim 5, wherein: theflexible printed circuit includes a pair of cone-shaped depressions thatare recessed inward at both end portions in the first direction (Y); anda pair of external connection terminals of the lower leaf springprotrude and joined thereto by soldering in a state where the externalconnection terminals are housed in the pair of cone-shaped depressionswithout protruding over a main surface of the flexible printed circuit.7. The lens holder driving device according to claim 6, wherein: theflexible printed circuit has a grounding pattern at a center portion onthe external surface side thereof; the first plate part of the yoke hasa protrusion part protruding downward at the first cutout part; theflexible printed circuit is attached on an exterior wall of the firstprotruding part of the base member in a state where the flexible printedcircuit is inserted in the protrusion part; and the yoke and thegrounding pattern are joined together by soldering at the protrusionpart.
 8. The lens holder driving device according to claim 7, whereinthe protrusion part is Sn-plated and half-punched.
 9. The lens holderdriving device according to claim 3, wherein: the ring-shaped upper endpart of the yoke includes a semi-punched portion that is semi-punched ata plurality of portions on an inner periphery side of the ring-shapedupper end part; and the upper leaf spring makes contact with theplurality of semi-punched portions when the lens holder moves upward.10. The lens holder driving device according to claim 3, wherein: thevertical extending part of the inner housing has a protrusion protrudingoutward in a radial direction; and the yoke is fitted to the innerhousing in a lightly pressed state with the outer cylinder part of theyoke pushing down the protrusion of the inner housing to thereby set aposition of the yoke with respect to the inner housing.
 11. The lensholder driving device according to claim 10, wherein the protrusion hasa substantially semi-columnar shape which extends in a directionparallel to the direction of the optical axis (O).
 12. The lens holderdriving device according to claim 11, wherein the protrusion has a topend portion having a substantially half cone shape at an upper partthereof.
 13. A camera-equipped mobile terminal in which the lens holderdriving device according to claim 1 is installed.